1. Field of the Invention
The present invention relates to a method and an apparatus for forming glass fibers by feeding molten glass onto the bottom wall of a spinning cup, whereby the glass is urged by centrifugal force outwardly along the cup bottom wall and upwardly on the cup side wall for extrusion through holes in the side wall. The general method is sometimes referred to as rotary fiberizing.
2. Prior Art Developments
Our issued U.S. Pat. No. 4,767,431 relates to a method of forming glass fibers wherein solid glass pellets are deposited onto a rotating spinner disc heated to maintain the pellets in a semi-solid state. The softened pellets are thrown outwardly by centrifugal force against a side wall on the disc periphery. The soft semi-liquid glass is extruded outwardly through small holes in the disc side wall into a downflowing stream of hot gas surrounding the spinning disc structure. The extruded glass fibers are thereby turned or deflected for downflowing movement with the hot gas stream. The hot, gas pulls or stretches the individual fibers so that the fiber diameters are reduced or attenuated to a desired size range.
In another version of the process, the glass material is deposited onto the spinning disc structure as a molten stream of glass, which remains in a molten state as it passes through the holes in the side wall of the disc structure. A problem with this method is the potential plugging of the holes (orifices) in the disc side wall. Unless the glass temperature is well above the devitrification point, the glass may crystallize, thereby plugging the extrusion holes (orifices).